1. Field of the Invention
The present invention relates generally to a television receiver, and more particularly, is directed to a television receiver in which a power supply source for a load circuit such as an audio output circuit and the like is derived from a horizontal deflection circuit or high voltage switching circuit.
2. Description of the Prior Art
There has been proposed a system in which a power supply source for, for example, an audio output circuit is obtained from a horizontal deflection circuit or a high voltage switching circuit which has substantially the same construction as the horizontal deflection circuit.
As shown in FIG. 1, a prior art circuit in which the power supply source for the audio output circuit is derived from the horizontal deflection circuit will be described. The prior art circuit includes a horizontal output transistor 1, a damper diode 2 connected in parallel with the collector-emitter path of transistor 1 a resonant capacitor 3 connected in parallel with diode 2, and a series circuit of a horizontal deflection coil 4 and an S-shaping capacitor 5 connected in parallel with diode 2. In the circuit of FIG. 1, there are further provided a fly-back transformer 6 having a primary winding 6a and a secondary winding, and a DC power supply source 7 which is connected between ground and transformer 6 and which supplies power voltage through primary winding 6a of fly-back transformer 6 or choke coil to the collector of transistor 1.
Further, a horizontal drive circuit 8 is provided through which a horizontal oscillation output from an input terminal 9 is applied to the base of horizontal output transistor 1 to turn transistor 1 ON and OFF. When transistor 1 is turned OFF, a fly-back or retrace pulse is obtained at the collector of transistor 1. This fly-back pulse is voltage-double-rectified by a high voltage rectifier circuit (not shown) at the side of secondary winding 6b of fly-back transformer 6 and derived as a high voltage.
In the circuit of FIG. 1, an audio power supply transformer 10 is connected in parallel with fly-back transformer 6 and, at the secondary winding side thereof, the fly-back pulse is rectified by a rectifier circuit 11 as a low voltage rectifier output which serves as the power supply source for the audio output circuit.
With the above prior art circuit, since audio power supply transformer 10 is connected in parallel with both fly-back transformer 6 and horizontal deflection coil 4, the pulse voltages of deflection coil 4 and fly-back transformer 6 are modulated by the output from the audio output circuit, which results in flicker of the reproduced picture.